It is known to incorporate an intumescent seal within the stile or frame of fire resistant doors. Typically, the door stile includes an inner strip of mineral material, such as a cast gypsum mixture, an intermediate intumescent strip seal, and an outer strip or band of hardwood or the like. When subjected to elevated temperatures, as experienced in a fire, the intumescent strip seal expands to seal the air space between the door frame and the door.
One problem with fire resistant doors has been the screw holding ability of such stile constructions, particularly along the inner edge of the door stile where the door hinges are secured. It is critical that the screw-holding capacity of the stile remain intact under the highest temperatures in a fire situation in order for the intumescent seal to function properly and keep the door fixed to the frame.
This invention provides a new high density strip configuration that substantially increases the screw-holding capacity of the door stile, achieving high ratings of screw withdrawal according to the standard NWWDTA TM-10 Test. To achieve such a rating, the present invention, in one exemplary embodiment, locates the intumescent seal strip within an edge groove formed in the door stile, after having first inserted a strip of high density material in the base of the groove. This strip of high density material anchors the hinge screws and is itself protected against flaming by the inorganic material of the stile that surrounds the high density strip on three sides, and by the intumescent strip that closes the groove under the outer hardwood edge or lipping.
The door stile construction may be formed by fixing the strip of high density material and the intumescent strip seal within a machined groove in the stile, or by casting the door stile around the high density strip and the strip seal. In the latter case, the intumescent strip seal is preferably laminated to the high density strip, and the latter is slightly wider than the intumescent strip seal in order to firmly lock the high density strip within the stile.
Accordingly, in its broader aspects, the invention relates to a fire resistant door edge construction comprising a stile having a groove formed therein, opening along one edge of the stile, a high density strip located in and extending along the groove; an intumescent strip seal adjacent the high density strip; and an edge lipping extending along the one edge, covering the intumescent strip seal.
In another aspect, the invention relates to a fire resistant door edge construction comprising a stile having a high density strip embedded within an edge of the stile, the high density strip partially surrounded by the stile; an intumescent strip seal adjacent the high density strip; and an edge lipping extending along the one edge, covering the intumescent strip seal.
In still another aspect, the invention relates to a fire resistant door comprising a door frame, a core, and veneer panels or plywood doorskins covering front and back faces of the door frame; the door frame including a stile extending along an inner edge of the door frame, the stile having a groove formed therein, opening along one edge of the stile, a high density strip and located in and extending along the groove; an intumescent strip seal adjacent the high density strip; and an edge lipping extending along the one edge, covering the intumescent strip seal.
In still another aspect, the invention relates to a fire resistant door comprising a door frame, a core, and veneer panels or plywood doorskins covering front and back faces of the door frame; the door frame including a stile extending along an inner edge of the door frame, the stile having a high density strip embedded within an edge of the stile, the high density strip partially surrounded by the stile; an intumescent strip seal adjacent the high density strip; and an edge lipping extending along the one edge, covering the intumescent strip seal.
In still another aspect, the invention relates to a method of forming a door edge comprising:
a) providing a laminate comprising a strip of high density material and an intumescent strip seal, each having a predetermined width, wherein the width of the strip of high density material is greater than the width of the intumescent strip seal; and
b) casting a stile member about the laminate such that a face of the intumescent strip seal lies substantially flush with one edge of the stile member; and
c) covering the one edge with an edge lipping.
In still another aspect, the invention relates to a method of forming a door edge comprising:
a) providing a strip of high density material having a base portion with a width greater than a remaining portion;
b) casting a stile member about the strip of high density material such that one face of the high density material is substantially flush with one edge of the stile member; and
c) covering the one edge with a laminate comprising an intumescent strip seal and an edge lipping extending along substantially the entire length of the one edge.
Other objects and advantages of the subject invention will become apparent from the detailed description that follows.